[kube-monitoring] Auto-discovery of Alertmanager configuration

[richardtief]

Context

Users who install a kube-monitoring plugin in Greenhouse remote cluster and there is already an alerts plugin in the central cluster, the alertmanager configuration should be preconfigured automatically.

Tasks

• feed alertmanger url
• use the secret to read the certificate Authentication on alert manger input

  optionValues:
    - name: alerts.alertmanagers.hosts
      value:
        - alertmanager.domain.dns
        - alertmanagerdomain.dns
    - name: alerts.alertmanagers.tlsConfig.cert
      valueFrom:
        secret:
          key: tls.crt
          name: organisation-prometheus-sso-cert
    - name: alerts.alertmanagers.tlsConfig.key
      valueFrom:
        secret:
          key: tls.key
          name: organisation-prometheus-sso-cert